x86: fix prefetch workaround

some early Athlon XP's and Opterons generate bogus faults on prefetch
instructions. The workaround for this regressed over .24 - reinstate it.

Signed-off-by: Ingo Molnar <mingo@elte.hu>

diff --git a/arch/x86/mm/fault.c b/arch/x86/mm/fault.c
index fdc667422df9913f2f5d861a3e80fad14eab7f4d..c0c82bc143c98966e9e5e88634560096b5ae4923 100644 (file)
--- a/arch/x86/mm/fault.c
+++ b/arch/x86/mm/fault.c
@@ -92,7 +92,8 @@ static int is_prefetch(struct pt_regs *regs, unsigned long addr,
        unsigned char *max_instr;
 
 #ifdef CONFIG_X86_32
        unsigned char *max_instr;
 
 #ifdef CONFIG_X86_32

-       if (!(__supported_pte_mask & _PAGE_NX))
+       /* Catch an obscure case of prefetch inside an NX page: */
+       if ((__supported_pte_mask & _PAGE_NX) && (error_code & 16))

                return 0;
 #endif
 
                return 0;
 #endif